Building muscle and strength doesn't require a gym membership, or even weights, according to a new study from the University of Texas-El Paso. In a new test of manual resistance exercises, where a training partner provided the resistance, researchers found the strength training to be just as effective as using weights.

During a 14-week period, the scientists monitored 84 college students who were assigned to either a traditional program of weights-based exercises, or manual resistance workouts. Both groups were given six exercises and performed eight to 12-rep sets two to four times. By the end of the study, the two groups showed no significant differences in strength development.

And while many of us do have regular access to strength training equipment, manual resistance can be especially helpful when you're traveling or can't make it to the gym. Basic strength moves like a squat would be performed with your training partner's hand on your shoulders, pressing down. Or to add resistance to push-ups, your spotter stands over you, pressing down on your back. For bicep curls or shoulder presses, hold a towel in your hands while your partner pulls down on the ends.

Any pair of adults can perform manual strength exercises, and they don't need to be of equal strength. In each exercise the spotter can use his or her body weight for a mechanical advantage.